Enhancing the luminescence of Mn4+-doped double perovskite oxide Ca2LuNbO6 phosphor by utilizing A-site cationic fluoride as a flux

Abstract

Supplement illumination is indispensable in the indoor plant cultivation domain. In this research work, double perovskite Ca2LuNbO6:Mn4+ phosphors were produced. A strategy of enhancing luminescence performance by utilizing A-site cationic fluoride as a flux was proposed. The structure and morphology of Ca2LuNbO6:Mn4+ phosphor was characterized. Under the excitation of 360 nm, the emission spectra of Ca2LuNbO6:Mn4+ phosphor cover from 600 nm to 750 nm peaking at 683 nm. It benefits the red section of chlorophyll absorption band and possesses the wavelengths of 680 nm and 700 nm demanded by photosystem I (PS I) and photosystem II (PS II) to realize Emerson enhancement effect. After adding CaF2 as flux, the emission intensity increases by 2.5 times. Due to its compatibility with the A-site cation of host, CaF2 agent not only lower the sintering temperature but also increase the crystallite size, which result in the enhancement of luminescence. The Dq/B and optical band gap of Ca2LuNbO6 host is 2.32 and 3.79 eV, respectively, which show that Mn4+ ions locate in the [NbO6] octahedra of strong crystal field and host has the suitable optical band gap for Mn4+ ions. With the help of CaF2, the thermal stability, activation energy ΔEa, internal quantum efficiency of Ca2LuNbO6:Mn4+ phosphors are promoted at 373 K from 64.8% to 70.7% of that at 273 K, from 0.33 to 0.36 eV, and from 9.1% to 23.5%. The luminescence lifetime of Ca2LuNbO6:Mn4+ is the order of a fraction of a millisecond. Finally, the as-prepared Ca2LuNb0.996O6:0.004Mn4+ phosphor was successfully fabricated through a 365 nm near ultraviolet (NUV) chip, which has the peak wavelengths of 683 nm and possesses 680 nm and 700 nm demanded by PS I and PS II. It is implied that Ca2LuNbO6:Mn4+ phosphor-converted light emitting diode has prospective market in the domain of supplement illumination of plant cultivation.